Did you run with -snes_test_display it will display the matrices computed both ways so you can see which entries are different and maybe track down the problem.
Barry On Aug 29, 2011, at 6:39 AM, Milan Mitrovic wrote: > Ok... I had a problem with indexing (-1 offset) in the local to global > mapping and now I get the following: > > Testing hand-coded Jacobian, if the ratio is > O(1.e-8), the hand-coded Jacobian is probably correct. > Run with -snes_test_display to show difference > of hand-coded and finite difference Jacobian. > Norm of matrix ratio 3.24883e-07 difference 3.24883e-05 > Norm of matrix ratio 3.25662e-07 difference 3.25662e-05 > Norm of matrix ratio 3.26517e-07 difference 3.26517e-05 > [0]PETSC ERROR: SNESSolve() line 2255 in src/snes/interface/snes.c > > so I guess this means that it is slightly wrong :) > > can you explain now what it is doing here (and why I get this > error)... can I make it try to solve the equation with the > approximated fd jacobian (is it doing that already?)
